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Why should you be supplementing with Vitamin D?


Why should you be supplementing with Vitamin D?

Another of the very few supplements I recommend (and sell here at CrossFit Thumos) is Vitamin D. Vitamin D’s bone-building benefits are widely known. But in addition to building strong bones, it turns out that this vitamin does much, much more. Vitamin D controls over 1000 processes in your body. When you are completely deficient, you end up with dysregulation of mineralization in your bones. This is known as rickets. Modern day rickets is rare, but that certainly doesn’t mean we are all getting enough vitamin D. Suboptimal levels don’t allow your body to function at its best, and chances are, you’re not getting enough.


Without an optimal level, you miss out on several extremely important processes in your body. This includes regulating immunity, decreasing type II diabetes, decreasing cancer rates, decreasing dementia, increasing fertility and positive sex hormones, improving gut function and decreasing overall inflammation.

Vitamin D also prevents aging and problems with cell division. Telomeres are the caps on the long strands of your DNA that prevent aging. These generally shorten when cells divide. When measured, the length of telomeres are a direct sign of cell aging. The shorter your telomeres, the older your cellular age. Studies have found that vitamin D helps protect against DNA damage and prevents cellular aging by protecting the lengths of your telomeres.

If you’re an athlete, you’re intentionally shredding your tissue. Your body needs to adapt to the demands placed on it. You are going to need an ever higher protection against inflammation, improved sex hormones and buffer for cell division and growth. Vitamin D helps with all of this. Many athletes are not getting enough.


Over 75% of Americans are deficient in vitamin D. This figure is probably much higher after accounting for those who are not technically deficient, but are still not at an optimal level. With respect to vitamin D, minimums are established to protect bone mineralization, but not to help regulate 1000 other bodily functions. Up to 95% of people are not in an optimal range of vitamin D.This means that up to 95% of Americans are missing out on the myriad of processes that vitamin D regulates and improves.


Vitamin D synthesis from the sun is widely variant. The darker skinned you are, the lower the rate of vitamin D synthesis you will have. Season, proximity to the equator, clothing and sunscreen can all modify the synthesis of vitamin D as well.

If you’re like a typical American who sits inside most of the day then goes home after work and sits inside until the sun sets, you should probably supplement. If you’re an athlete looking to take full use of recovery and reduction of inflammation, then almost certainly. If you’re a light skinned individual who works an outdoor job near the equator, then you can probably skip supplementing.

The easiest way to figure out if you should be supplementing – get some blood work done. Anything under 25 ng/mL is technically deficient, yet still very far from an optimal level. Optimal levels for serum vitamin D are actually 65-75 ng/mL.

If testing is not available in your area or is too expensive for you, that’s fine- vitamin D isn’t. Since it is a fat soluble vitamin, you can take too much of it, but that would likely be difficult. Don’t go over 3000IU/25 lb body weight.


Vitamin D is a fat soluble vitamin. This means a few different things. If you take supplemental vitamin D, do so with fat. Without fat, the bioavailability is decreased, rendering the supplement significantly less useful to your body.

This also means that if you are overweight, you are going to need a higher dose than those with less body fat. The fat solubility concentrates in your adipose tissue, meaning you need more to allow it to get to the end organs and glandular tissues and make positive changes in your body.


So how much should you take? Look for roughly 1000-1500 IU per 25 pounds of body weight. If you have more fat mass, take a little more. Look towards supplementing in the morning as sometimes vitamin D can be stimulatory. Your brain and body is going to think you’re synthesizing a lot of UV rays, which implicate your circadian rhythm. And remember, supplementing with fat is key.

My recommended choice for a vitamin D supplement is PurePharma’s D3. They have doses that are reasonably high and mix the D with coconut oil to maximize absorption. Check out our review for PurePharma’s D3 here.

As highlighted above, supplementing with vitamin D is probably a good idea for most people. Most people don’t take enough as the RDI is far too low. Drawing your blood is the only way to know with certainty whether you need to supplement, or how much you need. But it wouldn’t hurt to start adding some in the meantime.

And at $17 for a three month supply, why the hell not?